1. Field of the Invention
This invention relates to the preparation of 8-hydroxy-quinoline by reacting o-aminophenol with acrolein or an acrolein derivative in the presence of an oxidizing agent.
2. Description of the Prior Art
French Patent 977,687 describes a variation of Skraup's reaction for preparing quinoline compounds. In particular, a process for preparing 8-hydroxyquinoline is disclosed in which o-aminophenol is reacted with acrolein in the presence of a mineral acid and an oxidizing agent such as o-nitrophenol, the acrolein being introduced preferably as a vapor which may be diluted with nitrogen. The yields are of the order of 60%.
In a process for producing 8-hydroxyquinoline described in Japanese Pat. No. 16,948/70, published Aug. 11, 1970, o-aminophenol is reacted with an acrolein derivative, such as allylidene diacetate, in the presence of a mineral acid and an oxidizing agent. When o-nitrophenol is employed as the oxidizing agent, the conversion of the phenols to 8-hydroxyquinoline is about 60%.
Japanese Patent No. 12,745/73, published Apr. 23, 1973, discloses the synthesis of 8-hydroxyquinoline by introducing acrolein into a mixture of o-aminophenol and o-nitrophenol, the o-nitrophenol being an oxidizing agent, in the presence of a mineral acid and a small quantity of an organic acid having a low molecular weight. The addition of the organic acid to the reaction medium retards the decomposition of the acrolein, and the product obtained is purer. The molar conversion of the total phenols into 8-hydroxyquinoline does not exceed 70%.